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<H1><A NAME="SECTION03150000000000000000">
LAPACK and the BLAS</A>
</H1>

<P>
LAPACK routines are written so that as much as possible of the
computation is performed by calls to the
Basic Linear Algebra Subprograms (BLAS)&nbsp;[<A
 HREF="node151.html#blas1">78</A>,<A
 HREF="node151.html#blas2">42</A>,<A
 HREF="node151.html#blas3">40</A>]<A NAME="765"></A>.
Highly efficient machine-specific implementations of the BLAS are
available for many modern high-performance computers. The BLAS
enable LAPACK routines to achieve high performance with portable code.
The methodology for
constructing LAPACK routines in terms of calls to the BLAS
is described in Chapter&nbsp;<A HREF="node60.html#chapperformance">3</A>. 

<P>
The BLAS are not strictly speaking part of LAPACK, but Fortran 77 code
for the BLAS is distributed with LAPACK, or can be obtained separately
from <EM>netlib</EM>.  This code constitutes the
``model implementation''&nbsp;[<A
 HREF="node151.html#blas2alg">41</A>,<A
 HREF="node151.html#blas3alg">39</A>].
<BLOCKQUOTE>
<TT>http://www.netlib.org/blas/blas.tgz</TT>

</BLOCKQUOTE>

<P>
The model implementation is not expected
to perform as well as a specially tuned implementation
on most high-performance computers -- on some machines it may give <I>much</I>
worse performance --  but it 
allows users to run LAPACK codes on machines that do not offer any other
implementation of the BLAS.

<P>
For information on available optimized BLAS libraries, as well as
other BLAS-related questions, please refer to the BLAS FAQ:
<BLOCKQUOTE>
<TT>http://www.netlib.org/blas/faq.html</TT>

</BLOCKQUOTE>

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<ADDRESS>
<I>Susan Blackford</I>
<BR><I>1999-10-01</I>
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